Personal Social Security accounts already exist!

Here's an interesting story I haven't heard before:

But privatized Social Security has been a fact of life for municipal employees in Galveston County, Texas, for nearly a quarter century. Local government workers voted overwhelmingly in 1981 to opt-out of Social Security in favor of a locally controlled system that has since been widely described as a phenomenal success.

Under federal law at the time, municipal workers had the option of not participating in the Social Security program, replacing it with private retirement accounts. The private system is subject to regular payroll deductions and employer matches, essentially mirroring Social Security tax withholding and employer match provisions.
...
Under Galveston's "Alternate Plan," the county withholds approximately six percent of each employee's salary for retirement. That money, along with a partial match by the county, is invested in personal accounts for each participating employee. The remaining county match covers the cost of disability and life insurance policies for employees, which also pay benefits much higher than those offered by Social Security.

Sounds an awful lot like my favorite proposed reform plan (even more than the President's), The Cato Institute's 6.2% Solution, in which workers can opt to divert their entire 6.2% portion of FICA taxes - in return for renouncing any claim to future payments from Social Security - while their employers will still pay their 6.2% portion of FICA into the Social Security account to pay current benefits. In case anyone's still confused, this is exactly how personal accounts will contribute to a shrinking of the SS deficit - revenues will still come in but future liabilities are reduced. Rasmussen Research released a poll in 1999 that over a third of younger workers would opt out of the system even if they never received a penny back from all the taxes they've already paid. Count me in that set.

One more quote from the story about the Galveston Alternate Plan:

Amid growing enthusiasm for an alternative to Social Security, the Democrat-controlled Congress voted in 1983 to end the provisions giving municipal workers the option to leave the federal system.

My question, even more than Why the heck did they end it after only two years? is Why the heck were only municipal workers allowed to do this and not regular joes like all of us and our dads and our grandmas?